Stirrup strap for mounting a horse



FIG. 1 is a front elevational view of a stirrup strap for mounting a horse illustrating my new design;

FIG. 2 is a side elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is a bottom plan view thereof. 

The ornamental design for a stirrup strap for mounting a horse, as shown and described. 